Piezoelectric crystal holder



P 1949- J. M. WOLFSKILL PIEZQELECTRIC CRYSTAL HOLDER 3 Sheets-Sheet 1Filed Aug. 7, 1947 JOHN M. WOLFSKILL Sept. 13, 1949. J. M. WOLFSKILLPIEZOELECTRIC CRYSTAL HOLDER Filed Aug. 7, 1947 s Shee'ts-Sheet 2 JOHNM. WOLFSKILL Sept. 13, 1949. J. M. WOLFSKILL 2,481,806

PIEZOELECTRIC CRYSTAL HOLDER Filed Aug. 7, 1947 I5 Sheets-Sheet 5 Fig 103 JOHN M. WOLFSKILL Patented Sept. 13, 1949 UNITED STATES PATENT OFFICE2,481,806 PIEZOELECTRIC CRYSTAL HOLDER John M. Wlfskill, Erie, Pa.Application August 7, 1947, SerialNo. 767,149

32 Claims.

This invention pertains to an apparatus for mounting piezoelectricquartz crystals, more particularly, it pertains to mounting thin highfrequency piezoelectric crystals to facilitate handling of suchcrystals, and provide improved performance over the prior art holders.

It is an object of this invention to provide contiguous electrodes ofvarying areas to elicit good response from piezoelectric crystals ondifierent harmonics.

It is another object of this invention to make good electrical contactsto plated electrodes of piezoelectric crystals at such a point or areaas to reduce the damping action of such contact as well as the contactresistance.

It is another object of this invention to provide a rigid support notonly for lateral movement of crystal blanks but also to prevent strainin the crystal blank due to its mounting or clamping supports.

Another object of this invention is to enable the crystal blank to beplated or loaded after mounting so that it may be adjusted to an exactoperating frequency by deposition of additional metal over the baseplated electrode without removing it from its mounting, or have itsmounting afiect this frequency adjustment afterwards.

Another object of this invention is to enable the handling of quartzblanks lapped to as thin as .001" so that they may be rigidly clampedand mounted into the holder without breakage during the operation.

It is another object of this invention to provide rigid mounting meansof sufficiently small proportions, and of such materials that it may bereadil sealed in a hermetically sealed holder, so that no deleteriouseffects will be had on the unit from the effects of the support meansmaterials.

In the prior art the mounting of high frequency crystals eitherfundamental or harmonic type, was always associated with a largepercentage of breakage in the quartz blanks. This tiguous electrodes. Ithas been'found that with these contiguous electrodes better harmonicperformance is obtained, since the series capacity which is usuallyassociated withpressure type mountings where an airgap is employed,introvl5 was'particularly true of crystals WhlCh used con- 2 quencyresponse with less damping on the crystals oscillation.

Various methods have been employed in the prior art to mount such platedcrystals including that of small metal clips which make contact andsupport the crystal, small wire loops in which the crystal edge isforced between the adjacent turns of a spring type loop, and sleeve typesupports in which the crystal is slid between the open section.ofasmallslotted tube.

All of these methods have the disadvantage of stressing the crystalsbeyond its elastic limits and causing fracture. These stresses may causetwisting in the quartz blank, bending at the edges, chipping, etc.,resulting in'a defective unit. Such stressing may not necessarily takeplace during the mounting operation, but subsequent to it, by a slightdistortion in the external pin connection when the crystal unit isplugged into a socket; during the sealing operation, or during extremechanges in temperature over which most crystal units are required tooperate satisfactorily. All of this is particularly true on crystalblank-s less than .010 in thickness.

This invention overcomes all of these difficulties in a unique manner byproviding, first of all,

two flat surfaces between which the crystal blank is clamped on itsperiphery. Such peripheral clamping means may be either round, square orrectangular- The ceramic or clamping rings are first lapped on the sidethat contacts the-crystal and then a coating of silver is fired to thisflat lapped surface. Connection to this plated ring isalso fired ontothe ceramic on the inner circle and on the outer surface bringing thecon.- tact to the outside unlapped. side of the ceramic ring. The platedcrystal is then placed between these two annular supports, which arethen placed between two small spring clamps which hold the entireassembly together and make contact .to the plated crystalelectrodesthrough the silver plating that has been fired. onto theceramic. Small depressions or cavities are formed on the outside of therings to accommodate the spring clamps. This centers the entire assemblyand provides a rigid support for the crystal as well as its associatedceramic rings and contact means. If the crystal electrodes are platedover. the entire area of the blank, it is desirable to have the ceramicring silvered around the entire periphery. If, however, only a smallareaof the crystal is used for the crystal electrode it isv only necessaryto silver the lapped ceramic ring directly over the pigtail connectionto the central crystalelectrode. This is a particular advantage 3 onhigh frequency crystals used with high order of harmonics where it isdesirable to reduce the capacity of the crystal holder and anyextraneous capacity outside the activated electrode area to a minimum.

Various forms of plating can be used on the crystal electrodesthemselves, either evaporated, sputtered of fired spots of gold, silver,or aluminum. It is desirable from an electrolysis. standpoint and from acontact potential standpoint to provide the same metals for the platedelectrodes on the crystal as is used on the ceramic rings, sinces thesetwo metals contact and if they are dissimilar, contact potentials may beset upwhich might cause corrosion or disintegration at the point ofcontact of either one of the metals. Since silver or gold is easilyfired to the ceramic, silver or gold electrodes on the crystal providesan excellent combination.

Once the crystal blank is mounted, the entire holder assembly may beinserted into a metal evaporating plater and the unit may then be loadedwith evaporated metal to the desired frequency by having the crystaloscillate during the operation. This is a particular advantage on thincrystals because the crystal blanks need only be handled during theinitial mounting operation, and the incidence of fracture due torepeated handling is greatly reduced,

Other means of holding the two annular rings may be employed such asflat leaf springs. However, it is a feature of this invention to enablethe expansion of the springs by means of a simple expansion tool for theinsertion of the complete assembly into the spring clips.

Another feature of the invention is the peripheral clamping of theblanks. This has a tendency to eliminate spurious responses in thecrystal, and consequently small activity dips throughout a temperaturerange. It provides a definite electromechanical termination for the edgeor edges of the crystal blank.

Further details of this invention will be apparent to those skilled inthe art to which it relates from the following specification, claims anddrawing, in which briefly Figure 1 is a perspective view of the thinquartz crystal and mounting with the housing removed;

Figure 2 is a vertical sectional view through the quartz crystalmounting and housing taken along the line 2-2 of Figure 3;

Figure 3 is a view taken along the line 3-3 of Fig re Figure 4 is a sideview of one of the ceramic rings embracing the'quartz crystal;

Figure 5 is a sectional view along the line 5-5 of Figure 4;

Figure 6 is another side View of the ceramic ring showing the sideopposite to that shown in Figure 4;

Figure 7 is a modified form of ceramic ring;

Figure 8 is a sectional view of the ceramic ring taken along the line8-8 of Figure 'I Figure 9 is a sectional view taken along the line 9-9of Figure '7;

Figure 10 is a view showing the other side of the ceramic ring from thatshown in Figure 7;

Figure 10a is a view similar to Fig. 10 with only one coating 21 ofsilver or gold thereon;

Figure 11 is a view in fragmentary perspective of an embodiment of thisinvention housed in a glass tube, and

Figure 12 is a sectional View of the base of the tube shown in Fig. 11.

Referring to the drawings in detail, the thin quartz crystal I0 is shownembraced by a pair of ceramic rings I I that are disposed so as to clampthe circumferential portions of the crystal I0 therebetween by thespring action of the resilient wire supports I2. Each of the springclamps I2 is provided with projections I3 fitting into small cavitiesformed in the ceramic rings II so that the assembled rings and quartzcrystal are supported by the springs I2 in suitably rugged fashion towithstand handling such: as the unit will receive in the course ofordinary use. The mid portions I4 of the members I2 are bent into a loopto substantially encircle the upper ends of the contact pins I5 that aresuported on the base I6 of the housing by glass insulation beads I1.These mid portions I4 may be soldered or welded to the ends of the pinsI5 and the glass beads I! are also firmly joined both to the pins I5 andto the base IS. The whole crystal and mounting assembly is supported onthe base IG and enclosed in the housing IBa that fits into the grooveI8b formed in the base and may be soldered therein.

The piezoelectric crystal blank I0 may be employed for frequencystabilization, and generation and absorption of high or ultra-highfrequency electrical oscillations, This piezo-electric crystal blankconsists of a crystal element that may have a thickness as small as A ofan inch and the major faces thereof may be cut substantially parallel tothe X-axis of the mother crystal and at an angle between +20 and +40 tothe optic axis. An angle of 30' or 35 with respect to the optic axis hasbeen found satisfactory. However, other types of piezoelectric crystalcuts may be employed and these cuts may be either parallel to or at anangle with respect to the X-axis or the optic axis. Furthermore, thecrystal may be made of slightly convex contour and the surfaces of themajor faces of the crystal blank should be free from even minutedepressions.

Suitable electrodes I8 and I9 are provided to each major face of thequartz crystal II) by processes such as plating, sputtering, evaporationin vacuum and the like. The lead of electrode I8 is connected by asolder or silver connection 20a to a suitable metallic coating 20extending around one of the ceramic rings H in contact with theprojection I3 formed on one of the spring clamps I2 as shown in Figures1, 2 and 3 and the other electrode I9 is connected to a similar metalliccoating 2 I on the other ceramic ring I I contacting a projection I3 onthe other spring clamp I2. As a result the contact pins I5 areconnected, one to the quartz crystal electrode I8 through the metalliccoating 20 on a portion of one of the ceramic rings I I and the otherelectrode I9 is connected to the other pin I5 through the metalliccoating 2I on a portion of the other ceramic ring II. The electrodes I8and I9 are each preferably of an area that is small compared to the areaof each of the major faces of the crystal blank I0. For example in acrystal blank having a diameter about inch the diameter of the electrodemay be about A; inch. Furthermore, the electrodes I8 and I 9 may be ofthe same diameters or they may be of different diameters and the crystalblank may be of circular or rectangular shape or any other convenientshape. The electrodes may likewise be of circular, rectangular or otherconvenient shapes. Each of the electrodes [8 and I9 are provided with apig-tail connection, the pig-tail connection of the electrode I8 beingconnected through the globule 20a of solder or silver to the coating 20and one of the pins I2, and the electrode I9 being connected to asuitable f pig-tail connection to the coating 2 I, this coating 2I beingconnected also through a globule of solder or silver to th pig-tailassociated with theelectrode I9.

"Details of construction of the ceramic rings II are shown in Figures 4to inclusive, Figures 7 to 10 inclusive showing a modified form. InFigure 4 is shown a side view of a ring H such as shown in Figure 1 andthis ring may be made of various insulation materials such as syntheticporcelain, fused quartz; glass, as Well as synthetic resins. The rings II instead of being made of the materials set forth above may be cut fromquartz crystal material the same as-the piezoelectric crystal blank andin this case these rings may be out from blanks that are cutatsubstantially the same angle or angles at which the piezoelectriccrystal blank is cut so as to have a linear coefficient of expansion thesame as the piezoelectric crystal blank and thereby prevent any slippagebetween the rings II and the piezoelectric crystal blank I0 throughtemperature cycling referred to as hysteresis effect. Hysteresis effectmay be explained as follows. If the frequency of the piezoelectriccrystal blank is measured at room temperature and the temperature of thecrystal blank is then raised or lowered and then brought back to theinitial temperature and the frequencymeasured after this temperaturecycle, it is frequently found that the second frequency is no longerexactly the same as the initial frequency and that the initial frequencycan be restored by jarring the piezoelectric crystal blank or by takingit through a temperature cycle in the opposite direction.

One side of this ring I I is provided with a metallic coating 20extending at least partially around the ring so as to contact one of theelectrodes Is for example and this coating also extends into the cavity22 receiving the projection I3 of the sprin clamp I2 that is employedfor supporting the crystal assembly and connecting one of the crystalelectrodes to one of the pins I5. The other side of the insulation ringII is provided with 'acavity 23 for receiving one of the projections I 3of the other spring clamp I2. However, no metallic coating surroundsthis cavity inasmuch as no connection is to be made to the springclampI2 from this side of this insulation ring. The surface of the ring I 'Inext to the quartz crystal I0 is provided with a metallic coating 24that consists of silver fired to the surface of the ring and thissilvered surface engages the opposite surface of the quartz crystal.This silvered surface of each of the rings I'I may be used to cementthese rings directly to the opposite surfaces of the crystal blank IIIand for this purpose cements of various types including a lowtemperature fired silver bondin cement such as now on the market may beemployed. Both of the rings II are made in this manner and each of theserings is provided with a metallic'coating such as coating 22, thecoating of one ring making contact with one of the supporting clamps I2and the coating on the other ringmaking'contact with the othersupporting spring clamp I2. In Figures 8, 9 and 10 is illustrated a ring25 similar to the ring II except that the ring 25 does not engage thequartz crystal throughout its circumference inasmuch as the ring 25 hastwo cut-away I portions 26. -As a result only the silvered surfaces 2'!engage the corresponding surfaces of the quartz crystal. These silveredsurfaces 21 may be employed to cement the ring 25 to the oppositesurfaces of the crystal blank III and furthermore,

if desired, only oneof the projecting areas of the ring 25 need beprovided with a coating 21 as shown in Fig. 10a. These rings 25 areparticularly adapted for use with high frequency crystals employing highorder harmonics where it is desirable to reduce the capacity of thecrystal holder. The rings 25 are also provided with cavities 22 and 23for receiving ends I3 of the spring clamps and one of these cavities ofeach ring 25 is also provided with a metallic coating for the purpose ofconnecting the associated spring clamp I2 to an electrode of the quartzcrystal.

InFigs. 11 and 12 is illustrated an embodiment of this invention inwhich the piezoelectric crystal blank and associated members arepositioned in a glass housing 28 which may be similar to glass housingsprovidedto vacuum tubes. This glass housing is provided with a base 29sealed to the contact pins I5 that project out of the base and areadapted to be used for connecting the piezo electric crystal blank IIIto an electric circuit. These pins l5 are sealed to the glass base 29 inair-tight fashion and for this purpose various glass to metal seals maybe employed. The base 29 is sealed to the housing 28 around thecircumference of the base and this operation is accomplished by suitableglass working technique. The interior of the glass housing 28 may beevacuated if desired so that the piezoelectric crystal blank I0 may beoperated substantially in a vacuum or an atmosphere of inert gas such asneon. nitrogen, helium and the like, may be provided inside of thehousing.

While I have described this invention in detail with respect to apreferred embodiment, it is of course apparent that modificationstherein may be made without departing from the spirit and scope of thisinvention and therefore I do not desire to limit this invention to theexact details shown and described except as defined by the followingclaims.

What is claimed is: I

1. A piezoelectric crystal apparatus assembly for extremely thinpiezoelectric crystal blanks comprising a piezoelectric crystal blankhaving a thickness between 0.01 inch and 0.001 inch, means forreinforcing said crystal blank without substantially impairing theoperation thereof and means for'connectin said crystal blank to anelectrical circuit.

2. A piezoelectric crystal apparatus assembly for extremely thinpiezoelectric crystal blanks comprising a piezoelectric crystal blankhaving a thickness between 0.01 inch and 0.001 inch, means cemented tosaid crystal blank for reinforcing said crystal blank withoutsubstantially impairing the operationthereof and means for connectingsaid crystal blank to an electrical circuit.

3. A piezoelectric crystal apparatus assembly for extremely thinpiezoelectric crystal blanks comprising a substantially circularpiezoelectric crystal blank having a thickness between 0.01 inch and0.001 inch, ring-shaped means for reinforcing said crystal blank withoutsubstantially impairing the operation thereof and means for connectingsaid crystal blank to an electrical circuit.

4. A piezoelectric crystal apparatus assembly for extremely thinpiezoelectric crystal blanks comprising a piezoelectric crystal blankhaving a thickness between 0.01 inch and 0.001 inch, means for clampingsaid crystal blank for reinforcing said crystal blank withoutsubstantially impairing the operation thereofv and means for connectinsaidscrystal blank .to.:an;electricaltcira wit:

5. A: piezoelectric. crystal" apparatus assembly: for extremely thinpiezoelectric crystala blanks comprising a piezoelectriccrystal-blank-having a: thickness between: 0.01 inch and.0.001 inch,-means engaging peripheral portions of. said crystal blankifor;reinforcing said crystal blank without substantially impairingtheoperation thereof and meansvfor. connecting said crystal blank to anelectrical :circuit.

6. A piezoelectric crystal apparatus assembly for. extremely thin:piezoelectric crystal blanks comprising; a piezoelectric. crystal blank.havingv a. thickness between- 0.01 inch and 0.001 inch, ring shapedtlelements engaging peripheral: portions of said' crystal blank for.reinforcing; said crystal blank without substantially impairing the:operation thereof and means for: connecting saidicrystalblank to. anelectrical circuit.

'7. A: piezoelectric crystal apparatus assembly for extremely thinpiezoelectriccrystalblanks as set; forth inclaim. lwherein'the means forreinforcing thecrystal blank-comprises .ceramic elementsengagingonly theperipheral. portions of saidcrystal :blankmajorfaces, the surfaces ofsaid ceramic elements. .engaging;said major faces being lapped;

8; Piezoelectriccrystalapparatus comprising a thinpiezoelectric crystal.having a thickness be-. tween 0.01 inch and 0.001 inch, apair ofceramic rings; each 'of saidrrings having onesurface thereof lapped to ahigh degree of flatness, means for cementing the lapped, surfaces;ofeachof said rings .to'peripheral portions of the majorfaces of. saidcrystalblank forreinforcingsaid crystal blank, said ceramic ringseach'havingsmall holes in substantially; diametrically opposed portionsthereof; andspringmeans positioned in sa-idsmall holes for. supportingsaid crystal blank-and .said rings in assembled relation.

9. Piezoelectric crystal apparatusv comprising a thin piezoelectriccrystal of circular configuration having a thickness'between 0.01.inch'and 0.001 inch, a pair-of ceramic'rings, each ofesaid rings havingone surface-thereof lappedtoahigh degree of-flatness, means forcementingthe lapped surfaces of. each of said rings'tov peripheralportionsiof the maj or faces of said crystal blank. for reinforcing saidcrystal blank, said-ceramicrings each having small holes insubstantially. diametrically opposed portionsithereof; andspring'meanspositioned in said-smallholes for; supporting said crystal blank andsaid; ringsin assembledrela tion';

10: Piezoelectric crystal apparatus comprisinga thin: piezoelectric,crystal having athickness be tween 0.01 inch and :0.001 inch, .a pair10f .lceramic rings, each of said rings having one surface there-. oflapped to a high degree of'fiatness, means. for cementing the lappedsurfaces of" each: of said rings to peripheral portions ofthemajorsfaces of said crystal 'blank' for. reinforcing said crystalblank, said-ceramic rings each having smallholes in substantiallydiametrically opposed: portions thereof, resilientwire elements havingthe ends thereof lodged in-said small holes, and; means attached. tosaid wire elements for supportingsaid crystal blank andsaidmingsinassembled relation.

11. Piezoelectric crystal apparatuscomprisingiathinpiezoelectriccrystal, a pair of .ceramicrings, each of saidringshaving one; surface thereof lapped to a-highdegree offlatness,-means:for cc"- menting;the.-lapped:surfacespreach ofsaidrrings toperipheral portionspf the-.majorfacespf said crystal blankfor reinforcing saidlcrystal blank, said ceramic. rings: each having;smallv holes, in substantially diametrically opposed. portions thereof,and springmeanspositioned. in said small holes for supporting-saidcrystal blank and. said ringsin assembled relations.

12. Piezoelectric crystal apparatuscomprising a. thin. piezoelectriccrystal, a.- pair. of ceramic rings; eachiof said rings having onesurfacethere of-lapped-to. a highdegree of flatness, meansfor cementingthe-lapped. surfacesof each of said rings ,to peripheral. portions-of.the major. faces of said crystal blank. forreinforcing, said crystalblank, andmeans for supportingsaid crystal blank and-saidringsinassembledrelations.

1 13;- Piezoelectric crystal apparatuscomprisinga thin piezoelectriccrystal, a pair of :ceramic :rings, each: of said rings having; onesurface thereof lapped to. a high degree-ofxflatness; meansrforcementingthealapped.surfaces of eachof said rings .to peripheralportions of the major faces of said. crystal blankfor: reinforcing.said' crystal blank, said ceramic ringseach havingsmall holes insubstantially diametrically; opposedportions thereof, resilientwireelements having the ends thereof positioned in saidsmall. holes; andmeans attachedto said wireelements for supportingsaid crystal. blank andsaidrings-in assembled rela tions.

14. A. piezoelectric crystal apparatus assembly for extremelythinpiezoelectric crystal blanks comprisinga. piezoelectric crystal.blank having ;a thickness between 0.01 inch and:0.001 inch, a pair ofelectrodes for said crystal. blank cone tiguousto-the centralportions ofthe major faces ofsaidcrystaLblank, an .element'having substan+ tiallyfgreater /meehanical.strength than. said piezoelectriccrystal blankcemented toperipheral portions ofloneecfzsaidmajorfaces .of said crystalblank for strengthening said crystal blankand connectionsstosaid-electrodesfor connectingsaid crystal .blankto a'desired circuit:

15. A piezoelectric crystal apparatus-assembly forextremelythinpiezoelectric. crystal blanks comprising; a .piezoelectric crystal.blank having a thicknessbetween 0.01-. inches and.0.001 inches, a .pairof electrodes.- for: said .crystal blankcon tiguous to thecentralportionsof the major faces ofsaid-.crystal blank, elements having vsubstan-- tiallygreater. mechanical strength than said piezoelectriccrystal blanksengagingrperipheral-portions of: said. major faces. ofsaid: crystal; blank for strengthening said crystal blank and havingsaid crystal-blank therebetween, resilient members for engaging said.elements.' and. pressing said elementsragainst said crystalblank andconnections between. said resilient members: and .selectedrones of saidelectrodesfor connectingsaid-crystal.blank toa'desired circuit.

16. A piezoelectriccrystalapparatus assembly for extremely thin;piezoelectric crystal! blanks comprising, a piezoelectric crystal: blankhaving at thickness-between 0:01-inch and 0.0012inch'; a.- pairrof.electrodes for. said: crystal blankcon tinguous. to: the, central;portions; of the major facesof saidprystal blank; ring,-shaped;elementshaving substantially: greater mechanical strength thansaidzpiezoelectric crystal. blank, said ring shaped elements beingcemented: one. on each side of -.saidt.cr:ystal-blank:forengagingperipheral portions-of;saidmajor-faces of said crystal blankforrstrengthening said -.crystal blank 1 and holding said.crysta'1 blanktherebetweem resilient meme bersforengaging saidfelementsand pressingscas nos L.. 9 elements against/said crystal blank and connectionsbetween said resilient members and'selected ones of said electrodes forconnecting said crystal blank to a desired circuit.

.17. A piezoelectric crystal apparatus assembly for extremely thinpiezoelectric crystal blanks comprising a piezoelectric crystal blankhaving a thicknesslbetween 0.01 inch and 0.001 inch, a pair ofelectrodes for said crystalblank contiguous to the central portions ofthe major faces ofsaid crystal blank, elements having substantiallygreater mechanical strength than said piezoelectric crystal blankcemented to peripheral portions of-said major faces of said crystalblank for strengthening said, crystal blank and holding said crystalblank therebetween, resilient members for engaging said elements andpressing said elements against said crystal blank and connectionsbetween said resilient members and-selected ones of said'electrodes forconnecting said crystal blank to a desired circuit.

18. A piezoelectric crystal apparatus assembly for extremely thinpiezoelectric crystal blanks comprising a piezoelectric crystal blankhavin a thickness between 0.01 inch and 0.001 inch, a pair of electrodes.for said crystal blank contiguous to the central portions of the majorfaces of said crystal blank, ring-shaped elements having substantiallygreater mechanical strength than said piezoelectric crystal blankengaging peripheral portions of said major faces of said crystal blankfor strengthening said crystal blank and holding said crystal blanktherebetween, resilient members for engagin said elements and pressingsaid elements against said crystal blank and connections between saidresilient mem bers and selected ones of said electrodes for connectingsaid crystal blank to a desired circuit.

19. A piezoelectric crystal apparatus assembly for extremely thinpiezoelectric crystal blanks comprising a piezoelectric crystal blankhaving a thickness between 0.01 inch and 0.001 inch, means havingsubstantially the same coefficient of expansion as said crystal blankfor reinforcing said crystal blank without substantially impairing theoperation thereof and means for connecting said crystal blank to anelectrical circuit.

20. A piezoelectric crystal apparatus assembly for extremely thinpiezoelectric crystal blanks comprising a piezoelectric crystal blankhaving a thickness between 0.01 inch and 0.001 inch, means havinsubstantially the same coefficient of expansion as said crystal blankcemented to said crystal blank for reinforcing said crystal blankwithout substantially impairing the operation thereof and means forconnecting said crystal blank to an electrical circuit.

21. A piezoelectric crystal apparatus assembly for extremely thinpiezoelectric crystal blanks comprising a substantially circularpiezoelectric crystal blank having a thickness between 0.01 inch and0.001 inch, ring-shaped means having substantially the same coefficientof expansion as said crystal blank for reinforcing said crystal blankwithout substantially impairing the operation thereof and means forconnecting said crystal blank to an electrical circuit.

22. A piezoelectric crystal apparatus assembly for extremely thinpiezoelectric crystal blanks comprising a piezoelectric crystal blankhaving thickness between 0.01 inch and 0.001 inch, ringshaped insulationmeans having substantially the same coefficient of expansion as saidcrystal blank for reinforcin said crystal blank without substantiallyimpairing the operation thereof and 10 means for connecting'said crystalblank to an electrical circuit.

23. A piezoelectric crystal apparatus assembly for extremely thinpiezoelectric crystal blanks comprising a piezoelectric crystal blankhaving a thickness between 0.01 'inch and 0.001 inch, means havingsubstantially the same coefficient of expansion as saidcrystal blankengaging peripheral portions of said crystal blank for reinforcing said.crystal blank without substantially impairing the operation thereof andmeans for connecting said-crystal blank to an electrical circuit. I

24. A piezoelectric crystal apparatus assembly for extremely thinpiezoelectric crystal blanks comprising. a piezoelectric crystal blankhaving a low temperature coefiicient of expansion and having a thicknessbetween 0.01 inch and 0.001 inch, said crystal blank being cutat anangle between ,20 and 40 degrees with respect tothe crystalline opticaxis, means having substantially the same coefficient:of expansion assaid crystal blank for reinforcing said crystal blank withoutsubstantially impairing the operation thereof and means for connectingsaid crystal blank to an electrical circuit. a l

25. A piezoelectric crystal apparatus assembly for extremely thinpiezoelectric crystal blanks comprising a piezoelectric crystal blankhaving a low temperature coefficient of expansion and having a thicknessbetween 0.01 inch and 0.001 inch, said crystal blank being cut at anangle substantially 35 with respect to the crystalline optic axis, meanshaving substantially the same coeflicient of expansion as said crystalblank for reinforcing said crystal blank without substantially impairingthe operation thereof and means for connecting said crystal blank to anelectrical circuit.

26. Piezoelectric crystal apparatus comprising a thin piezoelectriccrystal blank having a thickness between 0.01 inch and 0.001 inch, apair of quartz rings, each of said rings having one surface thereoflapped to a high degree of flatness, means for cementing the lappedsurfaces of each of said rings to peripheral portions of the major facesof said crystal blank for reinforcing said crystal blank, and means forsupporting said crystal blank and said rings in assembled relation.

27. Piezoelectric crystal apparatus comprising a thin piezoelectriccrystal blank of circular configuration having :a thickness between 0.01inch and 0.001 inch, a pair of quartz rings, each of said rings havingone surface thereof lapped to a high degree of flatness, means forcementing the lapped surfaces of each of said rings to Deripheralportions of the major faces of said crystal blank for reinforcing saidcrystal blank, said quartz rings each having smal1 holes insubstantially diametrically opposed portions thereof, and spring meanspositioned in said small holes for supporting said crystal blank andsaid rings in assembled relation.

28. Piezoelectric crystal apparatus comprising a thin piezoelectriccrystal blank having a thickness between 0.01 inch and 0.001 inch, 9.pair of quartz rings, each of said rings having one surface thereoflapped to a high degree of flatness, means for cementing the lappedsurfaces of each of said rings to peripheral portions of the major facesof said crystal blank for reinforcing said. crystal blank, said quartzrings each having small holes in substantially diametrically opposedportions thereof, resilient wire elements having the 1 1:1 ends'thereoflodgedimsaid small-holes, and means attached to the said wireelementsfior supporting said :crystal blank *and "said *rmgs'inassembled relation.

29. Piezoelectric crystal "apparatus comprisinga"thin"piezoelectricrcrystal blarikra pairof rings having substantiallythe same-coem'cient o'f expans'ion as said"crystafblankfieach o'fsaidrings having one surface theredflappeiitoa high degree of'flatnesa'means for'cementingthe lapped surfaces'of each ofsaid*ringstojiperipheral portions ofthe -majori aces 'of'said crystalblank for reinforcing said crystal blank saici quartz'rings each "havingsmall holes in substantiallyniametrically "opposed portions thereof,"and sprin means positioned in said -sm'all 'holes for supporting saidcrystal blank -an'dsai'd rings in assembled relation.

30. Piezoelectric -crysta1-apparatus comprising *athin piezoelectriccrystaI bIank a-pair ofrings having substantially the same coem'cient ofexpansionassaid crystalblanheach of said rings having one surfacethereof lapped" to -a high "degreeof fiatness,"means for cementing thelapped surfaces of each ofsaidringsto peripheral portions of the majorfaces of said *crystal'blank for reinforcing said crystal blankpandmeans forsupporting "said "crystal blank and said =rings 'in assembled.relation.

31. Piezoelectric -crystal apparatus comprising a thin piezoelectriccrystal blank having a thicknessbetween 0.01 inch and "0.001 inh, a'pair of quartz rings, each of said wings "having one sur- Iace thereoflapped to a hi'g'hdegree of "flatness, means -for= cementing theiappflsuriza'ccesofleach of said-rings to "peripheraiportions of themajor faces "6f said "crystal blank for "reinforcing said crystalblankysaid quartz rings'each having small holes in substantiallydiametrically opposedportionsthereof,"and'springmeans' positioned insaid small holes for. supporting'said crystal blank and saidrings in'assembledrelation.

"32. A piezoelectric crystal mounting for 'extremely thin piezoelectric'crystal blanks comprisinga piezoelectric'crystal-blank having a lowtemperature coefficient of expansion 'an'd having a thiknessbetweenQOlin'ch'anii 01001 inch-said crystal blank being cut at-an angle of 30with respect' to the "crystalline optic axis, means havingsubstantially" the same 'coefiicient of expansion'as saidcrystalblankfor reinforcing said crystal "blank-without substantially impairing theoperation thereof and means for connecting said'crystalbianlctoan-electrical circuit.

JOHNM. W'OIFSKILL.

" REFERENCES CITED The iollowing references are of record-in the file ofthis patent:

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